Food packaging

ABSTRACT

The present disclosure relates to thermally insulating food packaging and more particularly to containers for storing or transporting food when the temperature of the food is significantly different to that of the surrounding environment. In particular, a food packaging material for enclosing food is described, the material including a first, moisture-permeable inner layer, a second, moisture-impermeable outer layer and a third, insulating moisture-tolerant layer disposed between the first and second layers and spacing the first and second layer apart, wherein the third layer has an undulating form including voids and wherein the first, second and third layers are arranged such that moisture emanating from food within the container passes through the first layer and the third layer and condenses on the second, moisture-impermeable outer layer.

BACKGROUND

Containers for food are used throughout the service industry, whether toserve food to a customer at a service outlet or to contain the foodduring transport in the case of home delivery services.

SUMMARY

The present disclosure relates to thermally insulating food packagingand more particularly to containers for storing or transporting foodwhen the temperature of the food is significantly different to that ofthe surrounding environment.

According to an aspect of the disclosure, there is provided a foodcontainer having a form suitable for enclosing food, the material of thecontainer including a first moisture-permeable, inner layer, a secondmoisture-impermeable, outer layer and a third, insulating,moisture-tolerant layer disposed between the first and second layers,the layers being configured so that moisture emanating from food withinthe container passes through the first layer and is retained within thethird layer, wherein the third layer spaces the first and second layerapart and is attached to the first and second layers to resist shearmovement between the first and second layers and provide rigidity to thefood container.

The middle layer, and in particular its attachment to the first andsecond layers, may contribute rigidity to the container, allowing thecontainer to be formed into a box. The insulating properties of themiddle layer, and optionally also the first and second layers, reducesthe transfer of heat between the inside and the outside of thecontainer.

The resistance to shear movement can be provided by fixing the first andsecond layers at various points to the third layer, in particular usingadhesive at the points at which the first and second layers meet thethird layer, or at intermittent regular points over the surface of thethird layer. The rigidity of the third layer then resists relativemovement between the first and second layers in the plane of the layers,which can provide a stable structure that can form a food container suchas a box.

According to an arrangement, the middle layer of the material mayinclude corrugated material. This, or other structures for the middlelayer, may provide a rigid container with voids which can retain airthat has permeated through the inner layer, and in particular cancontain condensed moisture to keep it away from the contents of thecontainer. Voids within the third layer are defined by walls or surfacesonto which moisture within the trapped air can condense. A mid-sizecorrugated material, such as a b-flute material, has been found to beparticularly suitable for a food container. Tighter corrugation canreduce the amount of moist air that is able to flow into the middlelayer whereas a less contoured corrugation decreases the surface areaavailable for moisture to condense and can reduce the ability of themiddle layer to retain its structural integrity.

Standard US corrugated flute parameters are set out in the table below:

Flute Flute Flutes per Flute thickness Flutes per thickness Designationlinear foot (in) linear meter (mm) A flute 33 +/− 3 3/16 108 +/− 10 4.8B flute 47 +/− 3 ⅛  154 +/− 10 3.2 C flute 39 +/− 3 5/32 128 +/− 10 4.0E flute 90 +/− 4 1/16 295 +/− 13 1.6 F flute 125 +/− 4  1/32 420 +/− 130.8

According to an arrangement, the middle layer may include treatedcorrugated paper or card. This may provide a rigid, moisture tolerantand recyclable middle layer of the container that is also compostable.

In one embodiment, the first layer is perforated. Perforations can beused to enhance the ability of the first layer to allow the passage ofmoisture, or moist air, therethrough. This may facilitate moisturereaching the middle layer of the container material, preventingsignificant condensation within the container, or significantdeterioration of the first layer, that may cause deterioration in foodquality.

In one embodiment, the inner surface of the outer, second layer includesa coating.

According to an arrangement, the outer layer of the container may berendered non-moisture permeable by means of a coating on the innersurface thereof. This may prevent the transport of moisture and heatacross the boundary of the container while not preventing the flow ofmoisture from inside the container to the middle layer of the container.

According to an arrangement, the coating on the inner surface of theouter layer may serve to enhance the insulation of the container. Thismay allow the temperature of the contents of the container to bemaintained at the original temperature for longer.

According to an arrangement, the coating on the inner surface of theouter layer may be an infrared (IR) reflective coating. This may reduceradiative heat crossing the boundary of the container.

According to an arrangement, the coating may include a vacuum depositedmetalized or metallic coating such as an aluminium coating. This mayprovide an IR reflective coating to prevent radiative heat loss whilealso being recyclable.

According to an arrangement, the inner layer may further include agrease resistant coating disposed on the inner surface of the innerlayer to inhibit grease or grease-like products from leaking out of ordamaging the container.

According to an arrangement, the grease resistant coating may include aplant based, water based substance. This may provide a recyclable greaseresistant layer.

According to an arrangement, the container may further include a heatsealable coating disposed on the inner surface of the inner layer orgrease resistant layer to assist in the manufacture of the container orfor use when serving food within the container. The grease resistantlayer may provide heat sealable functionality in some embodiments sothat only a single layer may be necessary.

According to an arrangement, the materials of the container may all berecyclable, biodegradable and/or compostable. This can reduce thenegative impact of such containers on the environment compared to theEPS materials. In particular, any of the containers described herein maybe manufactured without the use of any plastics based materials, or atleast avoiding the use of any non-recyclable plastics-based materials.

In one embodiment, the first layer, or a coating applied to the innersurface of the first layer, includes a material authorised for use withfood products.

It will be appreciated that the thickness and grammage of the threelayers may be adjusted according to the desired rigidity, strength,insulating and moisture-absorbing requirements of the particularcontainer. However, in some embodiments, the grammage of the third layerwill be at least 50 gsm. In a specific embodiment, the grammage of thethird lawyer can be at least 80 gsm. In some embodiments, the grammageof the third layer will be less than 300 gsm. In a specific embodiment,the grammage of the third layer can be less than 200 gsm. The grammageof the first layer will be at least 30 sgm. In a specific embodiment,the grammage of the first layer can be at least 50 gsm. In someembodiments the grammage of the first layer will be less than 300 gsm.In a specific embodiment, the grammage of the first layer can be lessthan 200 gsm. The grammage of the second layer will be greater than 30gsm. In a specific embodiment, the grammage of the second layer can begreater than 50 gsm. In embodiments, the grammage of the second layerwill be less than 300 gsm. In a specific embodiment, the grammage of thesecond layer can be less than 200 gsm.

While it will be appreciated that the container may take any shape orform that is suitable for carrying the intended food item, in onearrangement, the container may be in a clamshell form, including a topsection and a bottom section which can be closed to form an enclosed,for example fully enclosed, optionally generally sealed or airtightcontainer to trap moisture, emanating from the food, within thecontainer. By generally sealed or airtight, it is meant that there areno significant open vents or direct airflow passages in the closedcondition in normal use, and substantial flow of air is inhibited innormal use. However small gaps, perhaps of the order of a millimetre maybe present, particularly due to tolerances and as the container will bedeformable, and positive sealing against a pressure difference is notrequired.

Optionally, a permeability coating is provided on the first layer tocontrol the permeability of the first layer. Such a permeability coatingcould be used to reduce the permeability of the first layer to preventsaturation of the inner moisture-tolerant layer.

According to an aspect of the disclosure, there is provided a web ofmaterial for manufacture of insulating food packaging including a firstmoisture permeable, inner layer, a second moisture-impermeable, outerlayer, and a third, insulating, moisture tolerant layer disposed betweenthe first and second layers and spacing the first and second layersapart, wherein the third layer is attached to the first and secondlayers to resist shear movement between the first and second layers andprovide rigidity to the material.

Optionally, the first moisture permeable, inner layer is perforated.Optionally, a coating is provided on the inner surface of the secondlayer, wherein the coating renders the second layer moisture impermeableand/or enhances the insulating properties of the second layer.

According to an arrangement, a blank for forming a food packagingcontainer may be cut from a web of the material described above, theblank having folds or score lines formed therein to form an enclosedcontainer, for example a fully enclosed container, for containing a fooditem. In some embodiments, the blank may form a sealed or airtightcontainer.

According to an aspect of the disclosure, there is provided a method ofmanufacturing an insulating food packaging material, the methodincluding providing a first web of a first moisture-permeable material,providing a second web of a second moisture-impermeable material,providing a third web of a third insulating, moisture tolerant layerdisposed between the first and second layers and spacing the first andsecond layers apart and attaching the third layer to each of the firstand second layers to resist shear movement between the first and secondlayers and provide rigidity to the material.

According to an arrangement, the second web of materials may be renderedmoisture impermeable by depositing a coating, optionally a metallic ormetalized coating, on a surface thereof and wherein the moisturetolerant material is bonded to the coated surface. This preventsmoisture coming from a food item within the container escaping, keepingthe heat the moist air carries within the container. Furthermore, itcauses this moisture to condense within the container where the releaseof latent heat can be directed back towards the food item. Additionally,or alternatively, a coating may be provided to enhance the insulatingproperties of the second layer.

According to an arrangement, the moisture permeability of the first,inner layer is enhanced by perforating the first material, allowingmoisture to be carried into the middle layer where it can condense andthe latent heat released can be directed back towards the food item. Thefirst layer may be provided as a ready-perforated layer or may beperforated as part of the manufacturing process, enabling the degree ofperforation to be controlled to suit the end purpose of the web or thecontainer that is being manufactured. The first layer may be perforatedprior to being attached to the third layer or after attachment to thethird layer.

Optionally, the first material is provided with a grease resistantcoating on a surface thereof and the moisture tolerant material isattached to the other surface of the first material.

Optionally, the moisture tolerant material includes a treated corrugatedpaper-based material.

According to a further aspect, there is provided a flexible foodpackaging, the packaging including a first moisture-permeable innerlayer, the first layer including a plurality of perforations, a secondmoisture-impermeable outer layer having an inner and an outer surface,the second layer including a heat-reflective coating on the innersurface, and a third, insulating, middle layer, disposed between thefirst and second layers, the layers being configured so that moistureemanating from food within the container passes through the first layerand is retained within the third layer.

In one embodiment, the third layer includes a non-woven fibre,optionally a cellulose-based non-woven fibre.

In one embodiment, the second layer includes a moisture-impermeablecoating on the inner surface thereof, optionally wherein theheat-reflective coating includes the moisture-impermeable coating.

Moisture permeability of the first layer may be controlled byapplication of a permeable coating on the outer surface of the firstlayer.

In one embodiment, the heat-reflective coating includes a vacuumdeposited metalized coating.

Optionally, the first layer includes an inner surface and an outersurface and the inner surface further includes a grease-proof orgrease-resistant coating. In some embodiments, the grease-proof orgrease-resistant coating can include or consist of a plant based, waterbased substance.

In one embodiment, the first layer further includes an adhesive coatingover at least a portion of the surface, optionally wherein the adhesivecoating includes a grease-proof coating. The adhesive coating may be aheat sealable layer.

Optionally, the container consists of recyclable, biodegradable and/orcompostable materials. In such embodiments, the container may beentirely recyclable, biodegradable and/or compostable.

In a particular embodiment, the third layer is thicker than either ofthe first and the second layers. Optionally, the grammage of the thirdlayer is at least 50 gsm. In a specific embodiment, the grammage of thethird layer can be at least 80 gsm. Optionally, the grammage of thethird layer is less than 300 gsm. In a specific embodiment, the grammageof the third layer can be less than 200 gsm.

The first and second layers may include paper-based materials.

According to a further aspect, there is provided a web of material formanufacture of insulating food packaging including a first moisturepermeable, inner layer, the first layer including a plurality ofperforations, a second moisture-impermeable outer layer having an innerand an outer surface, the second layer including a heat-reflectivecoating on the inner surface, and a third, insulating, middle layer,disposed between the first and second layers.

A blank for forming a flexible food packaging container may cut from aweb according to the previous aspect, the blank having folds or scorelines formed therein to form a container, such as a bag, for containinga food item. In other embodiments, the blank may be used to form anenclosed container. In some embodiments, the blank may be used to form afully enclosed container (e.g., a sealed or airtight container) forcontaining a food item.

According to a further aspect, there is provided a method ofmanufacturing an food packaging material including the steps ofproviding a first moisture-permeable inner layer, the first layerincluding a plurality of perforations, providing a secondmoisture-impermeable outer layer having an inner and an outer surface,the second layer including a heat-reflective coating on the innersurface, and providing a third, insulating, middle layer, disposedbetween the first and second layers, the layers being configured so thatmoisture emanating from food within the packaging material passesthrough the first layer and is retained within the third layer.

Optionally, at least a portion of the first layer includes aheat-sealing coating, the method further including heat treating theheat-sealing coating to secure a plurality of layers of the foodpackaging.

In one embodiment, the heat-reflective coating includes a metalizedcoating.

Optionally, the heat-reflective coating is moisture impermeable.

In one embodiment, the first layer has an inner and an outer surface andis provided with a grease resistant coating on the inner surface,wherein the third layer is arranged adjacent to the outer surface of thefirst material.

Optionally, the first layer is provided with a permeability coating tocontrol the permeability of the first layer.

The food container, the flexible packaging or the webs of materialdescribed above may include a third layer having an undulating form.

The food container, the flexible packaging or the webs of materialdescribed above may also include a fourth, liner layer attached to thefirst, moisture-permeable inner layer. The fourth, liner layer may alsohave an undulating form.

Optionally, the third and fourth layers have an undulating form thatundulates in a sinusoidal form in two perpendicular directions over itssurface.

In particular, the third and fourth layers may have an undulating formincluding a cup and ball shape.

In one embodiment, the third and fourth layers are embossed.

Optionally, the fourth layer includes a moisture-permeable layer.

Optionally, the fourth layer includes a plurality of perforations.

Optionally, the fourth layer includes a grease-resistant coating.

One particular embodiment includes a food container having a formsuitable for enclosing food, the material of the container including: aliner layer having an undulating form and a plurality of perforations; afirst moisture-permeable, inner layer having a plurality ofperforations; a second moisture-impermeable, outer layer including aheat-reflective coating; and a third, insulating, moisture-tolerantlayer having an undulating form and disposed between the first layer andthe heat-reflective coating of the second layer; wherein the layers areconfigured so that moisture emanating from food within the containerpasses through the liner layer and the first layer and is retainedwithin the third layer; and wherein the third layer spaces the first andsecond layer apart and is attached to the first and second layers toresist shear movement between the first and second layers and providerigidity to the food container.

A further embodiment includes a flexible food packaging, the packagingincluding: a first moisture-permeable inner layer, the first layerincluding a plurality of perforations; a second moisture-impermeableouter layer having an inner and an outer surface, the second layerincluding a heat-reflective coating on the inner surface; and a third,insulating, middle layer, having an undulating form and disposed betweenthe first and second layers, the layers being configured so thatmoisture emanating from food within the container passes through thefirst layer and is retained within the third layer.

As the skilled person will appreciate, features of the food containerand the web from which it is made may also be applied to the flexiblefood packaging and the material from which it is made and vice versa.

DRAWINGS

The Detailed Description is described with reference to the accompanyingfigures. The use of the same reference numbers in different instances inthe description and the figures may indicate similar or identical items.

FIG. 1 shows an example clam shell food container.

FIG. 2 shows a clam shell food container that has been modified suchthat when the lid is closed the container is generally airtight inaccordance with example embodiments of the present disclosure.

FIG. 3 shows a three layered insulating material;

FIG. 4 shows a three layered insulating material where the middle layeris a corrugated material;

FIG. 5 shows a three layered insulating material where the middle layeris a corrugated material and an infrared (IR) reflective layer isdisposed on the inner surface of the outer layer;

FIG. 6 shows a three layered insulating material where the middle layeris corrugated material, an infrared (IR) reflective layer is disposed onthe inner surface of the outer layer and the inner layer is perforated;

FIG. 7 shows a three layered insulating material according to aparticular embodiment for making a box where the middle layer iscorrugated material, an infrared (IR) reflective layer is disposed onthe inner surface of the outer layer, the inner layer is perforated anda grease resistant layer is disposed on the inner surface of the innerlayer;

FIG. 8 shows a graph depicting water retention within containers formingthe example clam shell containers and an embodiment of the presentdisclosure;

FIG. 9 shows a graph depicting heat retention within containers formingthe example claim shell containers and an embodiment of the presentdisclosure;

FIG. 10 shows a three layered insulating material wherein the middlelayer is insulating, the inner layer is moisture permeable and the outerlayer is non-moisture permeable;

FIG. 11 shows the three layered material of FIG. 10 wherein the middlelayer is a non-woven fibre and a non-moisture permeable coating isdisposed on the inner surface of the outer layer;

FIG. 12 shows the three layered material of FIG. 11 wherein the middlelayer is a cellulose based non-woven fibre and an additional insulatingcoating is disposed on the inner surface of the outer layer;

FIG. 13 shows the three layered material of FIG. 12, furtherincorporating the non-moisture permeable coating of FIG. 11 and acoating on the outer surface of the inner layer;

FIG. 14 shows the three layered material of FIG. 13, further including aheat sealing layer disposed on the outer surface of the inner layer;

FIG. 15 shows the three layered material of FIG. 14 wherein the innerlayer is perforated;

FIG. 16 shows the material of FIG. 15 further including a greaseresistant coating disposed on the inner surface of the inner layer;

FIG. 17 is a schematic diagram of a material having a cup-and-ballprofile;

FIG. 18a is a schematic diagram of a 3-layer packaging material;

FIG. 18b is a schematic diagram of a 5-layer packaging material withouta reinforced layer;

FIG. 18c is a schematic diagram of a 4-layer packaging material;

FIG. 18d is a schematic diagram of a 5-layer packaging material having areinforced layer;

FIG. 19 is a schematic diagram of a 4-layer packaging material havingperforated layers;

FIG. 20 is a schematic diagram of the packaging material of FIG. 19incorporating a metalized layer;

FIG. 21 is a schematic diagram of a further 4-layer packaging material;and

FIG. 22 is a schematic diagram of a 4-layer packaging material in use.

DETAILED DESCRIPTION

Containers for food are used throughout the service industry, whether toserve food to a customer at a service outlet or to contain the foodduring transport in the case of home delivery services. A significantrequirement of these containers is maintaining the food at an acceptabletemperature, such as keeping hot food hot for the duration of delivery.Another problem, particularly with hot food, is that moisture from thefood may result in the food becoming soggy and unpalatable duringtransport if moisture is retained or may transfer significant heat awayif the moisture is allowed to escape.

Previous containers have been formed of materials such as expandedpolystyrene (EPS). However previous approaches have so far failed tosolve both problems in a satisfactory manner. For example, thepolystyrene box, while providing significant insulation if the box isclosed, fails to address the problem of moisture leading to soggy food.Alternatives where the food container allows the moisture to be lost tothe environment introduce significant heat losses. The disclosure isparticularly concerned with disposable containers. In addition to thesefood quality concerns, containers made of material such a polystyrenepresent significant environmental concerns due to the inability torecycle or compost the material. Containers of paper or card tend tohave lesser insulation and the card tends to degrade with moistureexposure, making them less suitable for longer storage, unless madeparticularly bulky.

For non-food items, desiccant materials, or pouches of desiccantmaterial, may be used to absorb moisture within a container. However,such desiccant materials are not safe for human consumption and are notsuitable for storage near to items of food or drink.

FIG. 1 shows an example clamshell food container 100. This is a designused in the food service industry for serving and transporting food suchas burgers. The container includes a top section 102 and a bottomsection 104 wherein these sections are joined by a flexible section 106which allows movement between an open state and a closed state. Theflexible section 106 is continuous with both the top 102 and bottomsection 104 and is made through pre-scoring or pre-creasing. In thisclam shell food container 100, the container is rigid as the material itis made from is rigid.

This choice of box design can assist in confining the heat, or indeedlack of heat, of any food product, placed in it. However, there is stillsignificant flow of air in and out of the box as the sides of the box donot effectively seal the box in its closed state. Using the example ofhot food placed in this container, the box does reduce the flow ofheated air from the food into the environment. This often carriessufficient moisture away from the food to prevent it becoming soggy andunpalatable however this flow of heated air also cause a reduction inthe insulating ability of the box.

FIG. 2 shows a different food container design 200. This design buildson the clamshell design and provides extended sides 202 on the bottomsection 104 of the container, allowing the box to be generally airtight, sealed or enclosed, wherein generally air tight means that thereare no large gaps or vents through which air can leave or enter thecontainer. This can be achieved by forming the container such that thebottom section 104 nests within the top section 102 such that there areno significant air gaps, at least when the container is not deformed.

The generally airtight nature of the container significantly reduces theflow of heat from or to the contents of the box as the conduction to theair and subsequent transport of heat via air is reduced. Additionally,as the container is generally airtight, meaning that there are nosignificant air gaps that would allow a flow of air, the moisture isretained within the container, where it will condense and release latentheat. This is a second mechanism that the generally airtight container200 causes that retains heat within the container.

Taking the example of hot food within the container, the problem ofmoisture control must be considered. Whereas previously the excessmoisture carried in the air could be carried away from the food withinthe box due to the unsealed nature of the box, this moisture is nowretained in the sealed box. The retention of this moisture leads toincreased condensation and the accumulation of liquid water within thebox, potentially leading to soggy and unpalatable food. This presents aproblem to service providers that require a method of serving food thatis to be transported or kept warm without reducing the appeal of thefood, whether by allowing it to go cold or soggy. This disclosure aimsto address this problem, along with others.

FIG. 3 shows the cross-section of a material including a moisturepermeable inner layer 304, a middle, insulating, moisture tolerant layer302 and a non-moisture permeable outer layer 300. As described herein,the middle layer 302 may also provide substantial rigidity to thecontainer, such as forming a box. This may be achieved by spacing theinner 304 and outer layers 302 with the middle layer and attaching theinner and outer layers to the middle layer to resisting shear movementbetween the inner and outer layers.

As an example of this material being used in a food container, we willconsider a container with hot food placed within. The contents of thiscontainer can lose heat by three mechanisms, namely convection (ortransport), conduction and radiation. The first of these is addressedthrough design of the container. As mentioned above, the sealed boxprevents the flow of heat via the air, out of the box, significantlyreducing the heat lost by convection. The second mechanism is addressedby the middle insulating, moisture tolerant layer 302. This is amaterial with a low thermal conductivity that slows the conduction ofheat across the boundary of the container.

With the improved retention of the heat and sealed nature of thecontainer, moisture retention becomes a significant issue. The materialdepicted in FIG. 3 attempts to overcomes these challenges through theuse a moisture permeable inner layer 304. This allows the humid, warmair to travel through the inner layer 304, into the moisture tolerantmiddle layer 302. The humid air is prevented from traveling through thenon-moisture permeable outer layer 300 and so can condense within themiddle layer 302. The design of this middle layer 302 is such thatmoisture can condense and the resulting liquid will not significantlyaffect the structure and/or insulating properties of the middle layer302, leading to the middle layer 302 being considered moisture tolerant.

The condensation of moisture in the middle layer 302 keeps the condensedwater away from the food, preventing it from going soggy, whilst alsokeeping the heated air within the container. As the water condensesthere will be a release of latent heat, this can be used further tomaintain the heat of the air within the container as some of it isradiated back into the container. Due to the properties of the moisturetolerant middle layer 302, the condensed water does not significantlyimpact the structural integrity of the container and the middle layer302 may continue to provide significant rigidity to the container. Thismay be achieved by treating the material of the middle layer 302 toachieve high moisture tolerance, such as sizing a paper middle layer302. As described herein, the material of the middle layer 302 may alsobe chosen based on its moisture tolerant properties.

One skilled in the art will readily appreciate that plastics materialsare generally non moisture permeable whereas cellulose and paper-basedmaterials are generally moisture permeable, unless treated. In addition,paper-based materials tend to degrade and lose structural integrity onexposure to moisture. As used herein, as will be appreciated by one ofordinary skill in the art of container manufacture, references to alayer being moisture permeable or impermeable or tolerant are intendedto be taken in the context of a food container intended for temporarystorage of a food product.

The first moisture permeable layer should be sufficiently permeable thatmoisture emanating from a food product can pass through it. Some ofcourse may be retained (it is not an open gap). One very simple test forthe required permeability is that if a layer of the material is placedover a beaker of water at boiling point, moisture will be visibly seento escape through the layer. In an embodiment, perforations are used toenhance permeability of a layer, such as paper treated to be grease ormoisture resistant and moisture permeable refers to the overallpermeability including perforations.

By moisture tolerant is meant that the material will not degradeunacceptably during the exposure to moisture in a normal application. Bymoisture impermeable or non-moisture-permeable is meant that in thecontext, moisture will not readily pass through the material in a normalapplication. Suitable tests for determining properties of the materialsused are those defined by the technical arm of the American Paper andPulp Association (TAPPI).

In one embodiment, air permeability or porosity of a layer is testedusing the TAPPI 547 Sheffield method for testing the air permeance ofpaper and paperboard. According to this standard, the air permeance of acircular area of paper is measured using a pressure differential ofapproximately 10 kPa. The method measures the air that passes throughthe test specimen, along with any possible leakage of air across thesurface. For the vacuum metalized liner of the outer (or second) layerof the present system, a porosity flow of less than 10 mL/minuteprovides an appropriate level of porosity.

Water resistance of a layer, in particular of the middle, or third,layer can be tested using the TAPPI 441 Cobb method for determining thewater absorptiveness of sized (non-bibulous) paper, paperboard andcorrugated fibreboard, which provides a procedure for determining thequantity of water absorbed by nonbibulous paper. According to thestandard, the water absorptiveness or Cobb value of the paper is themass of water absorbed in a specific time by 1 square meter of paper,board or corrugated fibreboard under 1 cm of water. In an embodiment,the middle fluted layer of the present system can absorb at least 20 gsmor 20 grams per square meter of the paper.

The outer vacuum metalized liner may also be tested to determine a levelof non-moisture permeability. In particular, the TAPPI 448 WVTR methodcan be used to determine the extent to which the outer, or second, layerprovides a barrier to water vapour. The TAPPI 448 Water VaporTransmission Rate of paper and paperboard is tested at a set temperature(of 23deg C.) and humidity (50% relative humidity) and a second layercan prevent the transfer of more than 50 g of water vapour per squaremetre per day under such a test.

To determine the grease resistance of the inner layer, or of a coatingapplied to the inner layer, the TAPPI 559 Kit method can be used. Thismethod measures the degree of repellence or anti-wicking of paper andboards that have been treated with agents that prevent wetting of thecellulose fibres of the material. Test solutions with components such ascastor oil, toluene, heptane and turpentine can be used in the test andthe material is given a test rating, or kit rating with a maximum valueof 12. In some embodiments, a grease resistant first or inner layeraccording to the present system has a kit rating of between 7 and 12.

In further embodiments, one simple exemplary test is that, afterexposure to moisture emanating through the first layer when placed overa beaker of water at boiling point for 30 minutes, the rigidity of thematerial (measured by a bending moment test) is at least 50% of itsoriginal value if the container is a box or the tensile strength is atleast 50% of its original value if the container is a bag.

As noted above, by moisture impermeable or non-moisture-permeable ismeant that in the context, moisture will not readily pass through thematerial in a normal application. One very simple test is that whenplaced over the second layer as described above, visible moisture is notseen to escape. As will be appreciated from the disclosure, the moistureimpermeable layer can be made from a material, such as a paper-basedmaterial, which is ordinarily permeable but is rendered impermeable by acoating, particularly a metallic barrier coating.

It will be appreciated that the layers co-operate. In embodiments, atest of the material is that when placed over a beaker of water atboiling point for 30 minutes with the first layer down and the secondlayer uppermost, the following is observed:—

-   -   1) visible moisture is not seen to pass through the material    -   2) at the end of the test period, the material has gained weight        due to moisture condensing within the third layer; and    -   3) the structural integrity of the material is not unacceptably        degraded, in particular the bonding of the layers has not come        apart and the rigidity (in the case of a box) or the tensile        strength (in the case of a bag) has not reduced below 50% of its        initial value.

For containers intended only to be used for very short term storage, forexample within a food service outlet, the duration of the test may bereduced, for example to 10 minutes. Likewise, for longer term transport,a longer duration and/or higher degree of final rigidity/tensilestrength may be specified.

Another simple test that a material has the desired properties is that,when placed over a container of water from which substantial evaporationis occurring, which may be at or close to boiling point for a given testperiod, which may be as little as 5 minutes, under equivalent testconditions the material will gain more weight due to condensation withinthe middle layer when the first, inner, permeable, layer is lowermost tothe water than when the second, outer, impermeable, layer is lowermost.

In some embodiments, such as the one depicted in FIG. 4, the insulating,moisture tolerant middle layer is formed of corrugated paper 400. Thisis an example material that provides the required rigidity such asdemonstrated in a material such as cardboard. The corrugation providesspace or voids for moisture to condense without being absorbed into thepaper and compromising the rigidity of the material. The use of a sizingor coating treatment of the corrugated paper improves the moisturetolerance of the paper material, allowing the water to condense in themiddle layer 400 of the container material without causing collapse orbreak up of the container. The sizing or coating treatment may usestarch, alkyl ketene dimer (AKD) or rosin to provide the requiredmoisture tolerant properties.

FIG. 5 shows the material of FIG. 4 with an additional non-moisturepermeable insulating layer 500 disposed on the inner surface of theouter layer 300. This is a feature which can help to prevent themoisture of the air within the container escaping to the surroundingenvironment, keeping the heat in. In addition to this property of thislayer, the layer can provide additional insulation to the container,further assisting in maintaining the temperature of the contents of thecontainer. This could be, for example, a layer that helps reduce theradiative heat loss from the container, such as an infrared (IR)reflective layer. This could be formed of any material which has good IRreflection properties, for example an aluminium foil or coating. A goodIR reflective layer may be formed by vacuum metallization of the outerpaper layer; this combined the required insulating properties withrecyclability and composability. It will be appreciated that a similarreflective (e.g., metalized) coating or liner may be applied to theinside of the outer layer in other embodiments of the food containersdescribed herein.

While the inner layer 304 is required to be moisture permeable, this canbe achieved in many ways. Firstly, the material could be a paper layer,which, without coatings, can often be considered moisture permeable.However, in some cases the moisture permeability of the chosen materialmay not be sufficient to achieve the desired transport of moisture awayfrom the food. This can be overcome by perforating 600 the inner layer304 of the container, allowing a greater air, and moisture, flow intothe middle layer of the container. This can be seen in FIG. 6 and helpsprevent the contents of the container from becoming soggy. Theperforation 600 of the inner layer 304 only allows the moisture awayfrom the food but not out of the container.

As the food contents of the container is likely to contain grease orother food material that has a liquid component, it may be beneficial toprovide a grease resistant layer 700 that prevents these materials fromseeping out of the container or causing degradation to the container.This can be seen in FIG. 7, in which a grease resistant layer or coating700 is disposed on the inner surface of the inner layer 304. Thecombination of a grease (and moisture) resistant coating on the innerlayer with perforations can allow moisture to pass through the innerlayer without significantly undermining the structural integrity. Itwill be appreciated that ordinary untreated paper or card is moisturepermeable but moisture tends to weaken ordinary paper or cardsignificantly and so where card is used for food containers, it tends tobe made much thicker and/or treated to overcome this issue.

FIG. 8 shows a comparison of the water loss between two examplecontainers and an embodiment of the disclosure. This graph 800 shows theweight of water remaining in food containers as a function of time after100 ml of boiling water is poured into each. The first example container(Example Container 1) represents an open clamshell container, the second(Example Container 2) represents a closed clamshell container andfinally data for an embodiment of the disclosure is shown where amodified closed clamshell is represented. As can be seen in the graph,the Example Container 1 loses water at a far higher rate and after 20minutes has lost over 4% of the initial mass of water. While this may beindicative that any food is less likely to be soggy as significantamounts of water have been removed, the loss of water is likelyaccompanied by a significant loss of heat which is not desirable.

Example Container 2 retains water far better than Example Container 1 asthe closing of the clamshell serves to reduce the flow of moist air fromthe container. However, there is still a loss of 2% after 12 minuteswhich can be improved upon. The embodiment of the present disclosureloses less water that both Example Container 1 and Example Container 2with only 1.75% of the water lost after 12 minutes. The modifiedclamshell used in the embodiment represented on the graph has extendedside on the bottom section that allow a better seal to be achieved whenthe container is closed.

FIG. 9 shows the data for the same Example Container 2 and embodiment asFIG. 8 but compares the air temperature within the container after 100ml of boiling water is added to each and the containers closed. Theembodiment of the current disclosure maintains a consistently highertemperature throughout the time frame of the experiment. After half anhour, the temperature within Example Container 2 has dropped anadditional 5° C. compared to the embodiment. This represents animprovement in the heat retention of the embodiment of over 10% whencompared to Example Container 2.

Based on both FIGS. 8 and 9, the present disclosure can be implementedin such a way that both the water and heat retention are better thanthat of the example clamshell containers.

As mentioned above, the material does not have to be rigid. The middlelayer may provide the largest contribution to the rigidity of thecontainer. This may be similar to cardboard and therefore the containermay represent a box, such as those depicted in FIGS. 1 and 2. In thisembodiment, the middle layer would separate the inner and outer layerand resist shear movement between the two layers. Alternatively, themiddle layer may be flexible, which can enable different types ofcontainer, such as bags, to be formed. As described in more detailbelow, to enable a more flexible material, the middle layer may beformed of a non-woven fibre. As the skilled person will appreciate,features described above in relation to the material used to form thecontainer may equally be applied to the more flexible material used toform the bag.

FIG. 10 shows a material including a first moisture permeable innerlayer 304, a second non-moisture permeable outer layer 300 and a thirdinsulating middle layer 1000 between the first and second layers. Thismaterial is suitable for forming a container for enclosing a food item.The first layer 304 allows moisture to transfer through into the middlelayer 1000 of the material, thereby reducing the amount of water thatcondenses in the container, in contact with the food. The middle layer1000 acts as an insulating layer and may additionally be moisturetolerant meaning that the condensation of moisture in the middle layerwill not significantly reduce the insulating effects or any structuralbenefits the middle layer provides to the container. The outer layer 300is non-moisture permeable to prevent moisture from escaping thecontainer which would cause the latent heat of the water condensation tobe lost to the environment. In contrast, adding this outer layer trapsthe moisture in the middle layer 1000 where it condenses and the latentheat can be directed back towards the food contents of the container.

The inner 304 and outer 300 layers could be a variety of materials. Dueto the required moisture permeability of the inner layer 304, the bestchoice is a paper although a permeable plastic layer could also be used.The outer layer 300 is similar in structure to the inner layer 304 andcould be made out of paper, plastic or other suitable materials.

The middle layer 1000 should be an insulating material such as expandedpolystyrene (EPS) or wool. In particular, wood or cellulose-based fibrescan be carded and needle punched to form a material that is wool-like inits structure. Such a material has a structural integrity sufficient toenable it to be formed with a consistent thickness of between 5 and 10mm and provided in a roll to a manufacturing process for manufacturingthe food containers described herein.

The main purpose of this material is to provide a layer of low thermalconductivity to reduce heat loss across the material of the container.The layer 1000 may be flexible such that the material can be made into abag for containing food. Therefore a non-woven fibre may be used such asmicro-slit paper, shredded paper, cellulose fibres or wool. To addressenvironmental concerns that come with disposable containers, the middlelayer 1000 may be chosen to be recyclable, biodegradable or compostable.There are some plastics that possess these qualities but a bettermaterial has been found in cellulose based non-woven fibres. Materialssuch as micro-slit paper provide the required insulation while beingmore environmentally friendly compared to the alternatives. Anadditional requirement of the middle layer 1000 might be that it ismoisture tolerant such that water can condense in the middle layer 1000and not significantly decrease its insulating properties or causesignificant structural damage.

FIG. 11 shows the previously described three layer structure with anadditional coating 1100 on the inner surface of the outer layer 300.This coating 1100 is non-moisture permeable, such that moisture from thebody of the container, that has permeated the inner 304 layer of thematerial, cannot leave the outer layer 300 of the container and remainswithin the middle layer 1000 of the bag. This causes a larger amount ofwater to condense and release latent heat within the container, helpingin keeping the food contents of the bag warm.

Many materials could be used for this coating 1100. The most common ofthese would be a plastic coating as waterproof plastic coatings can beeasily produced. Alternatively, a metal coating could be applied to theouter layer 300 to prevent moisture being transported across thematerial. This could be formed outside of the material and bonded to theinner surface of the outer layer 300 such as thin aluminium foil ordeposited directly onto the outer layer 300 by processes such as vacuumdeposition.

FIG. 12 shows the three layered structure as depicted in FIG. 10 withthe addition of an insulating coating 1200 that acts to enhance theinsulation of the material. This is optimally located on the innersurface of the outer layer 300 as water can permeate the material nofurther than this, therefore allowing the insulating coating to retainheat from the food and from the latent heat that the condensing moisturereleases.

This coating 1200 can be any material with a low thermal conductivitysuch as EPS or with infrared (IR) reflective properties such asaluminium foil. The latter of these is more effective as the middlelayer already acts as a low thermal conductivity layer and helps reduceconduction of heat from the container however it is not necessarily goodat retaining IR radiating emitted from inside the container. Therefore,there could be a more significant insulating contribution to be made byan IR reflective coating. This could be a metal foil that is formedseparately to the outer layer or a metal formed through vacuumdeposition such as the deposition of aluminium. The benefit of vacuumdeposition is the reduced amount of metallic material required.Additionally, if the outer layer is a recyclable paper, the vacuumdeposition of metal does not prevent the paper from being recyclable. Itis possible that the function of anon-moisture permeable layer 1100 andinsulating layer 1200 are combined into a single layer such as a vacuumdeposited aluminium coating.

FIG. 13 depicts the three layered structure of FIG. 10 along with boththe non-moisture permeable coating 1100 and insulating coating 1200described above and shown in the previous figures. In addition to this,there is an additional permeability layer 1300 on the outer surface ofthe inner layer 304. This allows for the finer control of moisturepermeability of the inner layer 304.

In particular, an additional permeability layer may be used to preventthe complete saturation of the middle layer 1000 of the material. Forexample, when the inner layer 304 is composed of a material with toohigh moisture permeability and excessive amounts of water would condensein the middle layer 1000, this permeability coating 1300 may be providedto reduce the effective moisture permeability or porosity of the innerlayer 304 and prevent structural or insulation problems. Alternatively,this inner layer 304 may itself be manufactured with the desiredporosity by design.

FIG. 14 shows the material of FIG. 13 with the addition of a heatsealing layer 1400 disposed on the outer surface of the inner layer 304.Such a layer is useful when it comes to forming the container itself asit allows for the three layers with appropriate coatings to be preparedand then heat treated to secure them to each other. The heat sealinglayer may be formed of polyethylene, or a plant based, water basedsubstance.

FIG. 15 shows the material of FIG. 14 wherein the inner layer 304 isperforated 600. This allows the moist air from inside the container toflow away from the food and into the middle layer 1000 where themoisture can condense.

These perforations 600 can vary in size and separation depending on thematerial of the inner 304 or middle layer 1000. They can be formedbefore the material is assembled, while a web of the inner layer 304 isseparate from the webs of the other layers. Alternatively, the innerlayer 304 may be perforated 600 when already combined into the materialof the container.

FIG. 16 shows the material of FIG. 15 with the addition of a greaseresistant coating 700 on the inner surface of the inner layer 304. Thishelps prevent grease or grease-like substances, which may be present ina food item that is enclosed in the container, from leaking into thematerial and causing damage and degradation of the material or structureof the container.

This layer can also be recyclable and/or compostable, which when all ofthe other materials are recyclable means that the whole container can beconsidered recyclable as a whole.

The materials described in FIGS. 10 to 16 do not have any restrictionsplaced on their rigidity, it is therefore possible that the material maybe flexible and could be formed into the shape of a bag. The shape ofthis bag may be that of a paper takeaway food bag. The bag may also betemporarily sealable through roll top closures, adhesives, slottedhandles or ties. This allows the bag to be sealed for transporting thefood, retaining as much heat as possible.

In many embodiments of the present disclosure, the inner and outerlayers are composed of paper. The paper used can include virgin fibresor recycled fibres and can be bleached or unbleached.

As described herein, the materials making up the containers may have anadditional grease resistant coating or layer, particularly on the innersurface of the inner layer. In one embodiment, acrylic acid emulsions,such as an acrylic acid ester, may be used. Such a coating may also beused to provide the heat-sealing functionality described above. However,for a recyclable container, wax and plastics-based coatings such aspolyethylene, are avoided. Furthermore, environmental considerationspoint away from using fluouro-chemical treatments that could be used toprovide grease-resistance to the container surface. Instead, a plantbased, water based substance is can be used that is recyclable andcompostable. Suitable substances includes palm oil, soya bean oil,engineered starches or other natural products. Furthermore, the coatingcan provide grease resistance ranging from KIT 5 to KIT 12.

It will be appreciated that some containers will require both an innergrease-resistant coating and a heat-sealing coating that enables thecontainer to be formed by holding together multiple layers of thematerial and heating them under pressure. In particular, material thatis used to form food bags will typically require both a grease-resistantlayer and heat-sealing layer. Both functionalities can be provided in asingle layer, such as by using an acrylic acid emulsion as describedabove.

In other embodiments, such as in the formation of clam-shell typecontainers, while a grease resistant coating may be useful, no heatsealing properties are required and a different type of grease resistantcoating may therefore be used.

The process of vacuum depositing aluminium on the inner surface of theouter layer includes the steps of applying a lacquer coating followed byvapour deposition of aluminium. Another lacquer top coat is thenapplied. As it is desirable to make the container recyclable and/orcompostable this lacquer coating is renewable and has a weight range of1 gram per square meter (gsm) to 3 gsm.

In some embodiments, grammages of each layer may be chosen. In a bagapplication, this could be 35 gsm to 150 gsm for the inner layer, 300gsm to 1500 gsm for the middle layer and 35 gsm to 150 gsm for the outerlayer. In a rigid container, such as a box, this could be 50 gsm to 150gsm for the inner layer, 50 gsm to 250 gsm for the middle layer and 50gsm to 150 gsm for the outer layer. These values can provide sufficientinsulation while not requiring excessive resources.

In the food service industry, food containers can be decorated withdistinctive markings and advertising. As described herein, the innersurface of the inner layer 304 and the outer surface of the outer layer300 of the container may also be prepared in such a way that they can beprinted on. This may involve the deposition of an additional layer thatcan receive printing ink.

With the growing desire for more environmentally friendly solutions, theneed for disposable food packaging and containers that are recyclable orcompostable is growing. In some embodiment of the current disclosure alllayers of the container may be recyclable or compostable. This can beachieved through the use of paper inner and outer layers withspecifically chosen grease resistant layer, additional insulating layersor sizing substance that are recyclable or compostable.

Features of another embodiment of a food packaging material areillustrated in FIGS. 17 to 21. In this embodiment, the middle (or“third”) layer in the material undulates in two perpendicular directionsacross the plane of the layer. FIG. 17 is a schematic diagram of a layershown from above illustrating the form of the layer in which the “+”symbol 1702 indicates a local maximum, or convex area of the surface,and the “o” symbol 1701 indicates a local minimum or concave area of thesurface. The surface of the material therefore undulates both across andalong the material.

In the embodiment of FIG. 17, each hollow and each raised portion has agenerally semi-circular cross section so that, if a cross section of thematerial is taken either along or across the material, the cross sectionhas a sinusoidal form as illustrated in the middle layer of FIG. 18a .Hence the material of FIG. 17 can be referred to as having a“cup-and-ball” form. The skilled person will appreciate that othercross-sectional shapes are possible, for example the hollow and raisedareas could have generally triangular or polygonal cross-sectionalshapes. The material can generally be described as an “embossed”material.

The material of FIG. 17 includes a paper-based product, such as paper,card or paperboard. The use of a paper or cellulose-based materialprovides an absorbent, lightweight, inexpensive layer that isstraightforward to shape into the desired profile, such as thecup-and-ball profile. Such a material can also be used in a flexiblepackaging, or can be made into a more rigid structure by attaching theouter surfaces of the cup and ball shapes onto upper and lower layers.Moreover, the material is a moisture-permeable material.

The material used for the middle layer, and its thickness, rigidity andstrength can be selected based on the desired properties and applicationof the final packaging. Moreover, the insulating properties of thematerial can be “tuned”, for example by increasing the number ofcup-and-ball embossings per unit area.

Specific designs of packaging materials that may be formed using the cupand ball material of FIG. 17 will now be described with reference toFIGS. 18-21. It will be appreciated that equivalent packaging structurescan also be formed using the corrugated middle layers described aboveand therefore features of FIGS. 18-21 can be applied to the corrugatedembodiments previously described.

FIG. 18a illustrates a 3-layer packaging material according to oneembodiment. This is similar to the corrugated-layered structuresdescribed above, but using the cup-and-ball embossed middle layer 1804of FIG. 17 instead of a corrugated or fluted layer. As described for thepreceding embodiments, the inner layer 1802 may be coated with agrease-resistant coating and may have perforations to enable watervapour to pass through the inner layer 1802 to the middle layer 1804 forabsorption. Moreover, the outer layer 1806 may be coated withgrease-resistant or water-resistant coatings and may have printed text,pictures or instructions on its external surface 1808. This is anon-reinforced packaging material.

FIG. 18b illustrates a 5-layer packaging material also without areinforced layer. In this embodiment, an additional absorbent, embossedmiddle layer 1810 and an additional moisture-permeable inner layer 1812have been added to provide further structural stability to the packagingand additional insulation and absorbency.

FIG. 18c is illustrates a 4-layer packaging material, which includes the3-layer material of FIG. 18a and a further inner undulating layer, orliner, 1814 arranged to be positioned next to the food or whatever isheld within the packaging. This additional liner holds the packagingcontents away from the moisture-permeable inner layer to reduce thechances of the packaging and food becoming damp and provides additionalinsulation for heat and absorption of moisture in the packaging. Theadditional liner is moisture-permeable and may be made of exactly thesame material as the middle layer 1804, which simplifies manufacture.However, in some embodiments, the material of the liner 1814 may differslightly from the material of the inner layer 1804, since it may beuseful to make the inner layer 1804 from a more absorbent material andthe liner from a stronger, more structurally stable material so that itretains its shape when the container contents (particularly warm, moistcontents) are placed upon it.

In many embodiments, the liner 1814 is treated with a grease-barrier orgrease-resistant coating to prevent staining when in contact with foodor other greasy products.

FIG. 22 illustrates one embodiment of the 4-layer packaging material ofFIG. 18c in use. In FIG. 22, a hot food item 1816 has been placed on theliner 1814 of the packaging material. Moisture and heat from the foodcirculates within the hollows or cups of the inner liner. Due to thecup-and-ball profile of the inner liner, however, the heat remainstrapped in the hollows of the liner and the food therefore retains itheat for longer. Moreover, since the liner 1814 is moisture-permeable,moisture released by the food passes through the liner 1814 and throughor into the inner layer 1802 and middle layer 1804 of the packaging.Some moisture may also be absorbed into the liner material. Since themoisture is absorbed away from the food, and the bottom surface of thefood is not entirely sitting on an absorbent layer, the food does notre-absorb moisture and become damp, even if the absorbent middle layer1804 absorbs enough water vapour that it becomes quite wet.

In summary, as illustrated in FIG. 22, this embodiment enables the useof an embossed surface to increase the air circulation between the areasof contact of the contained food article and prevent the build-up ofwater vapour.

FIG. 18d illustrates a 5-layer packaging material having a reinforcedlayer. The reinforced layer may be a thicker or heavier paperboard, suchas cardboard, or may be manufactured from another material. Since heatis trapped within the inner layers 1802, 1814 of the packaging andmoisture is trapped within the middle and outer layers 1804, 1806 of thepackaging, the additional reinforcing layer can be made of any materialthat is suitable for the intended use of the packaging, for example awooden, metal or plastic (such as expanded polystyrene) layer could beadded to create a more solid packaging container.

FIG. 19 illustrates the 4-layer packaging material of FIG. 18c havingperforated layers. As the skilled person will appreciate, perforatedlayers may be provided in any of the other embodiments described above.In some embodiments, the liner 1814, inner layer 1802 and middle layer1804 are all perforated to enable the moist air released by food withinthe packaging to pass as quickly and easily as possible through theinner 3 layers of the packaging to the moisture-absorbent middle layer1804, where it can be absorbed away from the surface of the food.

FIG. 20 illustrates the packaging material of FIG. 19 furtherincorporating a metalized layer. The use of a perforated, embossed liner1814 facilitates the removal of moisture away from food. In particular,the perforation in the inner liner 1814 allows for the quick transfer ofmoisture away from the inside of the packaging system to the metalizedouter-layer, maintaining food quality. As described above, the metalizedsurface of the outer layer prevents loss of moisture from the outersurface of the container and provides a surface that encouragescondensation of the moisture out of the air passing out of the inside ofthe container.

In one embodiment, the metalized layer includes a thin vapour deposit ofaluminium directly onto the surface of the paper or board. Vacuummetallization is considered recyclable and compostable by many publishedsources as opposed to transfer metallization. Hence use of a vacuummetalized top liner with a reflective surface orientated inside the packprovides a recyclable layer that can ensure containment of InfraRed (IR)energy through IR reflection whilst maintaining a printable outer layerfor packaging graphics.

By way of contrast, FIG. 21 illustrates heat loss from a further 4-layerpackaging material that does not include a metalized layer on the insideof the outer layer.

Use of a cup-and-ball embossed middle layer can increase heat retentionas compared to a corrugated inner layer by reducing the opportunity forheat to travel along the corrugated passageways and away from the food.

A particular embodiment provides a non-vented “airtight” box designusing corrugate materials with optimised insulative properties combinedwith material and design features that ensure the containment of heatenergy, both real and latent, to provide extended heat insulation whilstcontrolling relative humidity conditions within the packaging tomaintain food quality in terms of temperature and texture. Featuresinclude use of multilayer cup and ball board construction, specific packdesign to eliminate or minimize air gaps, use of perforated and moistureresistant middle ply, use of vacuum metalized top liner (outer layer)and use of a grease resistant perforated inner liner.

The embodiments described and illustrated in FIGS. 17-22 can bemanufactured using the manufacturing methods already described above. Inparticular, flexible or rigid packaging can be formed depending onrequirements by fixing the embossed middle layer within the outer andinner layers at many or only a few points across the packaging surface.

Once formed into a layered structure, the material can be cut accordingto pre-designed templates to form packaging bags or more rigid and“airtight” containers,

In particular, the arrangements and materials described and illustratedin FIGS. 17-22 can be used in the manufacture of the food packagingboxes already described above, and it will be appreciated that theaddition of further undulating layers can increase the stability andrigidity of the boxes.

Alternatively, the materials described above, in particular in relationto FIGS. 17-22, can also be used to form a flexible food packagingmaterial that may be used to wrap food or to form more flexiblecontainers such as bags to carry food.

Moreover, it is noted that features of the earlier embodiments, such asmetalized layers, perforations of various sizes and frequencies andmanufacture from biodegradable materials, can be applied to thepackaging manufactured using the embossed middle layer and liner.

What is claimed is:
 1. A food packaging material for enclosing food, thematerial comprising: a first, moisture-permeable inner layer; a second,moisture-impermeable outer layer; and a third, insulatingmoisture-tolerant layer disposed between the first and second layers andspacing the first and second layer apart, wherein the third layer has anundulating form comprising voids; wherein the first, second and thirdlayers are arranged such that moisture emanating from food within thecontainer passes through the first layer and the third layer andcondenses on the second, moisture-impermeable outer layer.
 2. The foodpackaging material of claim 1 wherein the third layer has a form thatundulates in two perpendicular directions across its surface
 3. The foodpackaging material of claim 1 wherein the third layer comprises anembossed layer.
 4. The food packaging material of claim 3 wherein thethird layer comprises a cup-and-ball embossed layer.
 5. The foodpackaging material of claim 1 wherein the third layer comprises acorrugated or honeycomb material.
 6. The food packaging material ofclaim 1 wherein the third layer is attached to the first and secondlayers to resist shear movement between the first and second layers andto provide rigidity to the food packaging material.
 7. The foodpackaging material of claim 1 wherein the first layer is perforated. 8.The food packaging material of claim 1 wherein the third layer isperforated.
 9. The food packaging material of claim 1 wherein the secondlayer comprises an inner surface and an outer surface, the third layerbeing arranged next to the inner surface of the second layer and thematerial further comprising a coating on the inner surface of the secondlayer.
 10. The food packaging material of claim 9 wherein the coatingrenders the second layer moisture impermeable.
 11. The food packagingmaterial of claim 9 wherein the coating enhances the insulatingproperties of the second layer.
 12. The food packaging material of claim9 wherein the coating is an infrared-reflective or heat-reflectivecoating.
 13. The food packaging material of claim 9 wherein the coatingis a vacuum deposited metalized coating.
 14. The food packaging materialof claim 1 wherein the first layer comprises an inner surface and anouter surface, the third layer being arranged next to the outer surfaceof the first layer, the material further comprising a grease resistantcoating disposed on the inner surface of the first layer.
 15. The foodpackaging material of claim 1 wherein the container consists of at leastone of a recyclable material, a biodegradable material or a compostablematerial.
 16. The food packaging material of claim 1 further comprisinga fourth, moisture-permeable liner layer attached to the inner surfaceof the first inner layer, the fourth liner layer having an undulatingform.
 17. The food packaging material of claim 1 further comprising atleast one further, insulating moisture-tolerant layer having anundulating form comprising voids.
 18. The food packaging material ofclaim 1 wherein the grammage of the material is less than 300 gsm.
 19. Amethod of manufacturing a food packaging material, the methodcomprising: providing a first web of a moisture-permeable material;providing a second web of a moisture-impermeable material; and providinga third web of an insulating moisture-tolerant material, the material ofthe third web having an undulating form comprising voids; arranging thethird web between the first and the second web, spacing the first andthe second webs apart; coupling the material of the third web to thematerials of the first and the second webs.
 20. A food packagingcontainer having a form suitable for enclosing food, the material of thecontainer comprising: a first, perforated moisture-permeable innerlayer; a second, moisture-impermeable outer layer having an inner and anouter surface and comprising a heat-reflective coating on the innersurface; and a third, insulating moisture-tolerant layer disposedbetween the first layer and the inner surface of the second layer andspacing the first and second layer apart, wherein the third layer has anundulating form comprising voids and wherein the third layer is attachedto the first and second layers to resist shear movement between thefirst and second layers and provide rigidity to the food container;wherein the first, second and third layers are arranged such thatmoisture emanating from food within the container passes through thefirst layer and the third layer and condenses on the second,moisture-impermeable outer layer.